Dental procedures can cause solid matter (e.g. bone chips, tooth particles, tissue fragments, pieces of amalgam, mercury, other toxic or hazardous chemicals, composite residual, fragments of porcelain restoration, zirconium, aluminum oxide, and cleaning paste that contains silica, etc.) to enter fluids (e.g. saliva, blood, and cooling water) that are present in the patients' mouth. The solid matter is removed from the mouth to prevent the patient from swallowing or aspirating it and prevent it from entering the suction or water waste lines. Removal of the solid matter necessarily entails removal of the fluids and gases as well. When such fluids and gases are withdrawn from the patient's mouth (as by a vacuum powered saliva ejector or a high-volume aspirator/evacuator (HVE)), this solid matter can cause difficulties for the dentist and for the patient especially when the patient is anesthetized. Additionally, the solid matter can clog the vacuum/suction system and water waste line so as to cause it to malfunction. Another such difficulty is that the solid, liquid and gaseous matters can be incorporated in an aerosol created during a dental procedure and the build up of the solid matter can occur on the inner surfaces of the vacuum/suction and dental unit lines and suction and water waste lines, thereby forming an area for the growth of bio-film that in turn promotes the growth of bacteria. For these reasons, it is known to provide a variety of strainer/filter units behind the ejector or high volume evacuator (HVE) aspirator and in the dental operatory unit as well as in the suction lines of a vacuum system. Dental unit trap, such as a chairside or inline trap, can be used in the cuspidor, suction and water waste lines and suction pump. However, such trap cannot effectively filter small amalgams and other solid, liquid or gaseous particles and unnecessarily expose dental professional and patients to amalgam (and its mercury vapors and methyl mercury) in the operatory. The strainer/filter unit for the filtration system of the present invention separates the solid matter from the fluids, thereby preventing amalgam and other particles from entering the dental unit, pipelines of the suction system and suction pumps that are connected to the water waste lines without significantly adversely affecting the suction flow. Conventionally, the saliva ejector or HVE aspirator and source amalgam separator with a strainer/filter unit is disposable. Optionally, the strainer/filter unit of the present invention that collects solid, liquid and gaseous waste may not be entirely disposable or parts of it may be sterilized and re-used.
At the present time, amalgam particles are comprised of approximately fifty percent (50%) mercury and its disposal is of great concern to the Environmental Protection Agency (EPA) of the United States. Several states, cities and local townships have enacted laws providing for mandatory guidelines that now require dentists and endodontists who perform procedures involving amalgam to have a device called an amalgam separator. Current amalgam separators are solid waste collectors and are connected to the terminal aspect of the suction line at their inlet port and to the motorized suction pump at its outlet port. There are four general types of amalgam separators—sedimentation, filtration, centrifuge and a combination of two or more of the foregoing types. Existing amalgam separators typically require professional installation and are costly to install and maintain. For example, the building or dental office may need to be reconfigured to accommodate the currently available amalgam separators and the amalgam separators and suction system needs to be routinely cleaned.
The amalgam separator must conform to the International Standards Organization (ISO) 11143 Standard so as to collect ninety-five percent (95%) of amalgam waste generated as being advocated by “Best Management Practice” of the American Dental Association to minimize amalgam waste particles from entering the water waste lines of the sewage system. Most recently, New York State (NYS) has enacted mandatory regulations for dentists who perform procedures involving amalgam to capture ninety-nine percent (99%) of amalgam particles generated. Other states also have regulations or are contemplating regulations concerning amalgam or dental waste collection.
A Master of Science Thesis, Environmental Science Programme 2007, by Ulla Jacobson-Hunt, DDS, DMD, from Sweden, entitled “Amalgam and Mercury in the Dental Setting and the Efficiency of Amalgam Separators” points to the deficiencies of prior art amalgam separators. The author reveals on page two that “in a clinical setting amalgam separators are less effective, and only provide 60% and up in collecting amalgam waste from a dental facility.” The author concludes on page 32 of her thesis “that the clinical efficiency of the amalgam separators currently in Sweden are not meeting the ISO 11143 Standard” and she further infers that more studies are needed as to the clinical efficiency as the ISO 11143 Standard was solely based upon laboratory testing of amalgam separators. It is interesting to note that Sweden has recently proposed banning the use of amalgam in its country. If the U.S. is to ban its use, it is estimated to cost the public's dental expenses of $8.2 billion during the first year. To trained investigators, the performance of mandatory devices should undergo both rigid clinical and laboratory testing and this applies most appropriately to amalgam separators to substantiate their efficacy and claims made for these devices. Laws are being enacted mandating the use of amalgam separators based upon faulty science and such laws are a burden to those dentists who perform procedures involving amalgam as well as being misleading to environmentalists, the EPA and waste water and sludge treatment plants.
Other investigators have noted that clinical evaluation of existing amalgam separators would be difficult to perform and an article by the American Dental Association (ADA) dated Aug. 5, 2005, entitled “Summary of Recent Study of Dental Amalgam in Waste Water” states that “measuring the exact amount of amalgam waste being generated and discharged from a dental office is a very difficult task. The discharge of amalgam waste into sewerage systems is complicated by the fact that this waste is generated on an intermittent basis with huge day-to-day and even minute-to-minute variations. Methods such as sampling from drain or sewer lines, or even collecting total waste over several days show huge variations that are difficult to extrapolate into total waste generated over a year. For these reasons, sampling dental office wastewater discharge does not provide either an accurate or reliable estimate of discharge.”
It is important to note that, often times, upon completion of placement or removal of amalgam, the vacuum valves of the HVE and the saliva ejector holders are shut off. This results in amalgam particles possibly settling within the dental units and the pipelines of the suction system and water waste lines and become embedded within the biofilm of the dental units and pipelines of the suction system and water waste lines so as to prevent the amalgam particles from reaching the attached conventional amalgam separator. Over a period of time, a narrowing of the lumen of these lines may occur. In such a situation the use of disinfectants such as sodium hypochlorite will change the accumulated amalgam particles into methyl mercury which is considered toxic and the most hazardous form of amalgam waste.
Further, it is important to note that when the vacuum valves, air compressor for tools and water lines are shut off after a procedure for a patient, microbial contamination of the dental unit and water lines can occur due to the “suck back” phenomenon, which may be partially embedded in an existing biofilm. When air compresses, water condensation forms in the pipes. When the suction force, air compressor and water are shut off, air (and all airborne contaminants) from the environment are drawn into the valves, pipes and water lines, respectively. Upon the subsequent usage of the vacuum valves, air compressor and water lines, the liquids, solids and airborne (or vapor) contaminants come into contact with the next patient. This “suck back” phenomenon increases the likelihood of dental acquired infections.
All existing amalgam separators must be clinically considered to be inadequate in meeting the ISO Standard 11143 as they are not removing 95% of the amalgam particles generated. Another problem exists with prior art amalgam separators in that it is necessary to maintain a pH in the range of 5 to 10 within the dental units and pipelines of the suction system. Although bleach is typically used in dental procedures (to sterilize and disinfect root canal or to etch the tooth for bonding or tooth whitening or bleaching), bleach cannot be used with existing amalgam separators because it would adversely affect the pH level in the pipelines of the suction system. A pH below or above the 5 to 10 range may adversely affect the amalgam particles attached to the biofilm or amalgam particles resulting from a procedure involving amalgam so as to possibly cause the release of mercury vapors or result in the production of methyl mercury that is toxic and considered the most hazardous particle form from amalgam.
Existing strainer/filter units have a number of disadvantages. First, existing strainer/filter units within the dental unit and suction lines of saliva ejectors and HVE aspirators are difficult, if not impossible, to sterilize. The Food and Drug Administration (FDA) regulations in the United States do not require the strainer/filter units to be sterile as well as the saliva ejectors and aspirators and they need only be cleaned, which in itself is labor intensive and not cost effective. Even if a particular dentist is motivated to sterilize a strainer/filter unit and aspirator before connecting them to the dental unit and vacuum systems, existing strainer/filter units and aspirators can neither be easily emptied nor cleaned and sterilized. Hence, the strainer/filter unit and aspirator/HVE or saliva ejector holders used during a dental procedure on a patient may be unsterile at the beginning of the procedure. In the worst case scenario, the strainer/filter unit, aspirator/HVE, saliva ejector holders, water lines and/or air compressor lines may contain solid, fluids and/or airborne (e.g. vapor) substances from prior patients. This poses a danger that substances and debris from dental procedures performed earlier in the day may cross-contaminate (as by back flowing solid or fluid as well as airborne substances into the patients' mouth or due to the suck-back phenomenon) who is undergoing a dental procedure later on that day. The Center for Disease Control (CDC) in the United States does recommend that all items entering the mouth be sterile but this is not mandated by law. The National Institute of Health (NIH) in the United States has established “Universal Precautions” and guidelines to prevent this type of cross-contamination. Therefore, if a dentist is motivated to use a sterile strainer/filter unit for each patient, the dentist must make a considerable investment in strainer/filter units and must incur increased operating expenses to clean and sterilize them. Secondly, existing strainer/filter units are not versatile (the saliva ejector shown in U.S. Pat. No. 3,890,712 by Lopez is an example of such a non-versatile device). Prior art strainer/filter units are designed to work only with a particular type of saliva ejector or aspirator and cannot easily be used with other types of similar devices. Thirdly, existing sterile strainer/filter units are relatively expensive. The Osseous Coagulum Trap being sold through Quality Aspirators of Duncanville, Tex., is an example of an expensive strainer/filter unit. Fourthly, the cost and time associated with emptying and replacing dental unit traps can be high. Lastly, existing strainer/filter units do not properly filter all amalgam particles (whether in solid, liquid or vapor form) and keep the amalgam from regurgitating. Due to the pore size of existing strainer/filter units, small particles of amalgam waste enter the dental units or cuspidors and water waste lines resulting in amalgam particles (solid, liquid or vapor form) accumulating within the dental unit and the suction lines and pump. Some amalgam particles in solid, liquid or vapor form never reach the conventional amalgam separators. Other existing strainer/filter units with some or all of the disadvantages discussed above are disclosed in U.S. Pat. Nos. 4,058,896, 4,265,621, 4,464,254, 5,078,603, 5,630,939, 5,779,649, 5,741,134, 5,922,614, 6,428,316, and 7,214,059 and U.S. Patent Application Publication No. 2004/0115590.
Applicant's prior patent, U.S. Pat. No. 6,183,254, discloses a strainer/filter unit that overcomes some of the disadvantages mentioned above by providing a device that can be attached to the aspirator holder or saliva ejector valve. The strainer/filter unit comprises a plastic frustum-shaped strainer within a housing that is capped. The plastic strainer disclosed has multiple openings for filtering. Additionally, this prior art device does not prevent regurgitation or back flow of the amalgam as well as other solids, fluids and airborne gaseous substances collected in the strainer/filter unit.
Therefore, there is a need for an improved disposable single use strainer/filter unit that will overcome these disadvantages and act as an amalgam solid, liquid and vapor collector at the source. The present invention is an improvement of Applicant's prior patent and existing prior art by providing an anti-retraction valve as well as the filter to be designed for solid, liquid and airborne substances to travel a tortuous path when passing through the strainer/filter unit.